Photosensitive material and method for making color-proofing films

ABSTRACT

A photosensitive material for making color-proofing films for multicolor printing is described, with 
     A) a transparent flexible support of plastic, 
     B) a photopolymerizable layer on (A) which contains 
     B1) a polymeric binder, 
     B2) a compound polymerizable by a free-radical mechanism, 
     B3) a compound which is capable of initiating the polymerization of (B2) under the action of actinic light and 
     B4) a dye or a color pigment in a primary color of the multicolor print, and 
     C) a thermoplastic adhesive layer which comprises at least one polymer which contains units (C1) with aliphatic side chains having at least 5 carbon atoms. 
     The material is processed by laminating to an image receptor sheet, exposure and peeling apart of support and image receptor sheet, the unexposed layer areas remaining together with the adhesive layer on the image receptor sheet. These steps are repeated with at least one further image in primary colors. The material provides for a reduction of the background stain in the non-image areas.

This is a divisional of copending application(s) Ser. No. 08/432,048,filed on Apr. 28, 1995 U.S. Pat. No. 5,492,791, which is a continuationof Ser. No. 08/168,120, filed on Dec. 15, 1993, now abandoned.

The invention relates to a photosensitive material, in particular aphotopolymerizable material, for making color-proofing films formulticolor printing. It also relates to a color-proofing method, inwhich a multicolor image is produced on an image receptor sheet from aplurality of images in primary colors in register. The images in primarycolors are made by laminating a photopolymerizable layer, colored in aprimary color of the multicolor print, to the image receptor sheet,exposure under the respective color separation, developing the image bypeeling off the support of the photopolymerizable layer together withthe non-image areas adhering thereto, and repeating the same steps witha photopolymerizable layer of another primary color.

Such a color-proofing method and a material intended for this purposehave been disclosed by U.S. Pat. No. 4,895,787. This material iscomposed of a transparent support, whose surface has preferably beenpretreated for adhesion promotion, a photopolymerizable layer whichcontains a dye or a color pigment in a primary color of the multicolorprint, and a thermoplastic adhesive layer, which can be activated byheating, on the photopolymerizable layer. After lamination to an imagereceptor sheet, the material is exposed through the support and thendeveloped by peeling the support and image receptor sheet apart. Theexposed areas of the photosensitive color layer then remain on thesupport, while the unexposed areas together with the complete adhesivelayer remain on the image receptor sheet. Thus, the method ispositive-working.

This processing method has the great advantage that it does not requireany alkaline or acidic solutions or any organic solvents fordevelopment, eliminating disposal thereof. A disadvantage of this methodis the background stain which appears in the non-image areas,particularly if the colors magenta and yellow are used. The backgroundstain is caused by residues of dye or color pigment which remain afterthe peeling-off step on the surface of the adhesive layer in the case ofunduly strong adhesion between the photopolymerizable layer and theadhesive layer. A further cause of the undesired coloration of thenon-image areas can be the diffusion of the dye or color pigment intothe adhesive layer, which diffusion takes place during the preparationof the material or during the lamination.

It was the object of the invention to reduce the background stainappearing in the non-image areas.

The invention relates to a photosensitive material for makingcolor-proofing films for multicolor printing with

A) a transparent flexible support of plastic,

B) a photopolymerizable layer on (A) which contains

B1) a polymeric binder,

B2) a compound polymerizable by a free-radical mechanism,

B3) a compound which is capable of initiating the polymerization of (B2)under the action of actinic light and

B4) a dye or a color pigment in a primary color of the multicolor print,and

C) a thermoplastic heat-activatable adhesive layer.

In the material according to the invention, the adhesive layer (C)comprises at least one polymer which contains units (C1) with aliphaticside chains having at least 5 carbon atoms.

The feature of the adhesive layer (C) is that the adhesion between itand the photopolymerizable layer (B) is reduced as compared with thoseadhesive layers which do not contain the polymers described. Thebackground stain is reduced due to the diminished adhesion between (B)and (C). The action of the polymer with units (C1) can be regarded asthat of an internal lubricant.

The invention also provides a method for making a multicolor image,which comprises laminating a photosensitive material of the nature andcomposition defined above by its adhesive layer (C) under pressure to animage receptor sheet, imagewise exposing through the support under acolor separation, peeling the support together with the exposed areas ofthe photopolymerizable layer off from the image receptor sheet andrepeating the steps of laminating, exposure and peeling-off with atleast one photosensitive material of another primary color and therespective other color separation.

Another embodiment of the process according to the invention comprisesapplying an adhesive layer (C) of the composition given above to animage receptor sheet, laminating a photosensitive material composed of atransparent flexible support (A) and a photopolymerizable layer (B) ofthe composition given above by the photopolymerizable layer to theadhesive layer (C), imagewise exposing the photopolymerizable layerthrough the support under a color separation, peeling the supporttogether with the non-image areas off from the image receptor sheet andrepeating the steps of

applying an adhesive layer,

laminating to a photosensitive material,

exposure and

peeling off

with at least one further photosensitive material and color separationof another primary color, the exposure taking place in register with thefirst image in primary colors produced on the image receptor sheet.

The thermoplastic adhesive layer (C) should have a softening temperatureof about 40° to about 200° C., preferably of about 60° to about 130° C.,and it can be applied from a dispersant, solvent or solvent mixture. Thepossible procedures are as follows:

a₁) The adhesive layer can be applied directly to the photopolymerizablelayer, if the latter is not incipiently dissolved by the dispersant,solvent or solvent mixture used.

b₁) The adhesive layer can also be initially applied to a temporarysupport and be transferred from there by lamination and subsequentpeeling-off of the support to the photopolymerizable layer or to theimage receptor sheet. In the case of transfer to the image receptorsheet, the photopolymerizable layer is then laminated in a second stepto the adhesive layer thus obtained.

c₁) The adhesive layer can be applied to the image receptor sheet anddried. The photopolymerizable layer is then laminated to the adhesivelayer thus obtained.

The direct application of the adhesive layer from solvents to thephotopolymerizable layer is preferred. Suitable coating solvents, whichdo not incipiently dissolve the photopolymerizable layer, are water and,depending on the composition of the photopolymerizable layer, aliphatic,alicyclic and aromatic hydrocarbons and alcohols as well as mixtures ofthese. Typical examples are hexane, cyclohexane, toluene, butanol orcyclohexanol. Many polymers can be applied from a dispersion; however,application from solution is preferred, aqueous solutions beingparticularly suitable.

The essential feature of the polymers contained in the thermoplasticadhesive layer (C) are side-chain aliphatic radicals having at least 5and preferably 7 to 20 carbon atom. These radicals can be saturated orunsaturated, preferably saturated, straight-chain or branchedhydrocarbon radicals which can be unsubstituted or substituted byhalogen atoms or lower alkoxy groups, preferably having 1 to 4 carbonatoms.

The polymer can be a homopolymer or copolymer of vinyl monomers whichcontain said side-chain radicals. Copolymers with units (C1) arepreferred, in particular those which contain these units in a proportionof about 5 to about 35% by weight

Examples of possible vinyl monomers which form the units (C1) are vinylesters of aliphatic carboxylic acids, for example of caproic acid,caprylic acid, capric acid, lauric acid, myristic acid, stearic acid,palmitic acid, 4-methoxyvaleric acid, 6-chloropelargonic acid,3,4-dimethylheptanoic acid, Versatic acid or of mixtures of these acids,vinyl alkyl ethers, for example vinyl hexyl ether, vinyl isoheptylether, vinyl dimethyldecyl ether etc., and also acrylates ormethacrylates of monohydric alcohols having 5 to 20 carbon atoms.

With advantage, the polymers used in the adhesive layer (C) are thosewhich contain units (C1) of the formula I ##STR1## in which R¹ is analiphatic radical having at least 5 carbon atoms,

X is ##STR2## R² is H or CH₃ and R³ is H or an alkyl group having 1 to 2carbon atoms.

Those copolymers of units (C1) and (C2) are preferred in which the units(C2) are of the formula II ##STR3## in which

R is an aliphatic radical having 1 to 4 carbon atoms, preferably 1 or 2carbon atoms, and

the other symbols are as defined for formula I.

Examples of compounds which polymerize to give units of the formula IIare vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrateand vinyl methoxyacetate; (meth)acrylates such as methyl methacrylate,ethyl acrylate and 2-chloroethyl methacrylate; and crotonates such asmethyl or ethyl crotonate.

Those polymers are particularly suitable which contain additional units(C3) with acid groups, for example carboxyl groups or salts thereof.Examples of unsaturated carboxylic acids capable of forming units (C3)are acrylic acid, methacrylic acid, vinylacetic acid and crotonic acid.

If the adhesive layer contains the preferred terpolymers, thesepreferably have a content from about 5 to about 35% by weight of units(C1), about 45 to about 92% by weight of units (C2) and about 3 to about20% by weight of units (C3). Polymers with about 15 to about 30% byweight of units (C1), about 55 to about 80% by weight of units (C2) andabout 3 to about 15% by weight of units (C3) are particularly preferred.The content of units (C3) is preferably at least of such a magnitudethat the polymer can be dissolved in aqueous-alkaline solutions andapplied from such a solution.

Those terpolymers are in general used as constituents of the adhesivelayer (C) whose 20% solution in ethyl acetate has a viscosity of about 4to about 12, preferably about 5 to about 9, mPas at 20° C. The viscosityis measured by means of a Hoppler viscometer according to DIN 53 015 andrepresents, under otherwise identical conditions, a measure of themolecular weight.

The proportion of units (C 1) in the polymer present in the adhesivelayer and its molecular weight must be carefully matched to one another.The aliphatic side chains of the units (C1) effect a reduction in theadhesion between the photopolymerizable layer (B) and the adhesive layer(C). The adhesion between said layers can be controlled in the desiredway by means of their quantitative proportion and their nature and alsoby the molecular weight of the polymer. Owing to the reduction inadhesion as compared with known adhesive layers with polymers havingshorter aliphatic side chains, all those properties are positivelyaffected which require a low adhesion between photopolymerizable layer(B) and adhesive layer (C), especially the background stain and thegloss of the color image as well as the ease of handling of the materialin the peel-apart development.

On the other hand, the adhesion must not be unduly reduced, since theresolution then suffers. This effect is compensated by reducing theproportion of units (C1) in the polymer or by adding a polymer whichdoes not contain any units (C1), and by increasing the molecular weight.As the examples show, a product having the desired property spectrum canbe obtained by a suitable choice of the abovementioned parameters.

The copolymers of units (C2) and (C3) are above all suitable as additivepolymers without units (C1). In general, a good combination ofproperties is obtained by additional quantifies of about 20 to about 50%by weight of these copolymers, relative to the total weight of thelayer.

Good results are also obtained with polymers which do not contain anyunits (C3). Since these polymers are soluble only in organic solvents,adhesive layers with such polymers can in general not be applied fromsolution to the photopolymerizable color layer, because most of theselayers are soluble in organic solvents. In this case, only the lesspreferred method is possible, in which the adhesive layer is prepared ina separate process step on a separate temporary support and transferredfrom there by lamination either to the photopolymerizable layer (B) orto the image receptor sheet.

In addition to the polymer described, with units (C 1) and, ifappropriate, a copolymer of units (C2) and (C3) or a homopolymer ofunits (C2), the adhesive layer can also contain further constituents ina smaller quantity, for example up to about 15 % by weight. Possiblesuch additives are plasticizers, adhesion promoters, residual solvents,flow agents, lubricants, antistatics, inert fillers, fluorescentbrighteners and/or UV absorbers. The layer weight of the adhesive layeris in general in the range from about 2 to about 30 g/m² and preferablyabout 4 to about 15 g/m².

The photopolymerizable layer (B) of the material according to theinvention contains, as essential constituents, a polymeric binder (B1),a compound (B2) polymerizable by a free-radical mechanism, a compound(B3) which forms free radicals and thus initiates the polymerization ofthe polymerizable compound (B2) under the action of actinic light, and adye or a color pigment (B4) in a primary color of the multicolor print.Examples of photopolymerizable layers of this composition are given inU.S. Pat. No. 4,895,787, which is incorporated herein by reference.

The polymeric binder (B1) is intended to confer homogeneity and strengthon the layer. Suitable binders are styrene/maleic anhydride copolymersand styrene/maleic acid half-ester copolymers, acrylate ester polymersand copolymers, polyamides, polyvinylpyrrolidones, cellulose derivativessuch as cellulose esters and ethers, phenolic resins, polyvinyl esters,polyvinyl acetals, for example polyvinyl butyral. propional or formal.The quantitative proportion of the binder is in general about 15 toabout 70 and preferably about 20 to about 50% by weight, relative to theweight of the solid layer.

The polymerizable compound (B2) contains at least one and preferably atleast two terminal double bonds polymerizable by a free-radicalmechanism and is not gaseous at temperatures below 100° C. and at normalpressure. Esters and amides of acrylic and methacrylic acid arepreferred. In particular, the esters with polyhydric alcohols areemployed with advantage. Examples are di-, tri-, tetra- andpoly-ethylene glycol di(meth)acrylate, the di(meth)acrylates of oligo-and poly-propylene glycols, 1,4-butanediol di(meth)acrylate,trimethylolpropane tri(meth)acrylate and trimethylolethanetri(meth)acrylate, pentaerythritol tri- and tetra-acrylate or-methacrylate, and dipentaerythritol tetra-, penta- andhexa-(meth)acrylate. The quantitative proportion of polymerizablecompound is in general about 15 to about 70 and preferably about 20 toabout 60% by weight.

Suitable photoinitiators (B3) are essentially all compounds or compoundcombinations known for this purpose. Examples are benzoin ethers, benzilketals, polynuclear quinones, benzophenone derivatives,triarylirnidazolyl dimers, and photosensitive trihalogenomethylcompounds, for example trichloromethyl-s-triazines.2,3-Bis-aryl-quinoxalines, such as are described in U.S. Pat. No.3,765,898, and 2-aryl-4,6-bis-trichloromethyl-s-triazines areparticularly preferred. The quantity of photoinitiator or photoinitiatorcombination is in general between about 1 and about 25 and preferablybetween about 5 and about 15 % by weight.

The dyes and/or color pigments (B4) are selected such that theycorrespond to the primary colors of the multicolor print, namely cyan(blue-green), magenta (purple). yellow and black. Pigments are ingeneral preferred. Examples are Permanent Yellow G (G.I. 21,095),Permanent Yellow GR (G.I. 21,100), Permanent Yellow DHG (C.I. 21,090),Permanent Ruby L3B (G.I. 15,850:1), Permanent Pink F3B (C.I. 12,433),Hostaperm Pink E (G.I. 73,915), Hostaperm Red-Violet ER (C.I. 46,500),Permanent Crimson FBB (C.I. 12,485), Hostaperm Blue B2G (C.I. 74,160),Hostaperm Blue A2R (C.I. 74,160) and Printex 25 (carbon black). Ifnecessary, the pigments can be blended to obtain the desired colorshade. The inorganic or organic pigments are in general dispersed orpasted together with a part of the binder in a suitable solvent. Themean particle size is in general below 1 μm, preferably below 0.2 μm.

The quantitative proportion of the dye or pigment or of the dye orpigment mixture is in general about 8 to about 40% by weight andpreferably about 12 to about 30% by weight of the photopolymerizablelayer.

If desired, the photopolymerizable layer (B) can contain furtherconstituents such as hydrogen donors, sensitizers, polymerizationinhibitors, plasticizers, residue dissolvers, surfactants,surface-leveling agents, lubricants, adhesion promoters, antistatics,inert fillers, fluorescent brighteners and/or UV absorbers. It has ingeneral a layer weight from about 0.2 to about 5 g/m², preferably about0.3 to about 3 g/m².

After drying of the photopolymerizable color layer, the adhesive layerwhich can be thermally activated is applied thereto in the mannerdescribed.

The supports used are transparent, flexible, dimensionally stable sheetsof plastics, for example polyesters, polycarbonates and the like.Particularly preferred are polyester sheets, in particular biaxiallystretched and thermofixed sheets, for example of polyethyleneterephthalate. These should remain dimensionally stable at the requiredlamination temperatures, i.e. from about 60° to about 150° C. Theirthickness is in general about 10 to about 200 and preferably about 25 toabout 80 μm. The support is advantageously given an adhesion-promotingpretreatment on one or both sides and can have a smooth or a roughand/or dull surface, preferably a smooth surface.

For carrying out the method according to the invention, thephotosensitive material described above is laminated by the adhesivelayer to an image receptor sheet. The latter can be composed of plastic,a plastic-coated special paper or of customary printing paper. Otherwhite and in some cases also non-white receptor sheets can also be used.A printing paper which is dimensionally stable under the laminationconditions is usually preferred, since a visual impression largelyapproaching the later print is achieved thereby. The lamination isadvantageously carried out in an apparatus intended for this purpose,under pressure and at an elevated temperature. The laminationtemperature is usually in the range of about 60° to about 130° andpreferably between about 80° and about 120° C. After the lamination, thephotopolymerizable layer is imagewise exposed through the support, ingeneral in contact under a positive color separation, in the knownmanner. After the exposure, the support is peeled off by hand or in asuitable device. The peeling angle should be at least 90° , and an angleof 180° is particularly preferred. In this way, the exposed areas of thephotopolymerizable layer are removed together with the support, whilethe unexposed areas remain on the image receptor sheet together with theentire adhesive layer. In this way, a positive image in primary colorsis obtained. Every further color-proofing film is laminated in themanner described to the preceding image in primary colors, exposed,preferably in register, and developed by peeling off the support.

The invention is explained by the examples which follow. All percentagedata and quantitative proportions are to be understood in units byweight. In Examples 1 and 2, photosensitive materials with adhesivelayers according to the state of the art are described. Examples 3 to 8serve to illustrate the advantages which result from the use ofphotosensitive materials according to the invention.

The synthesized polymers are characterized in each case by measuring theviscosities of a 20% solution in ethyl acetate (at 20° C., HOpplerviscometer, DIN 53 015), and via the glass transition point Tgdetermined by differential thermal analysis using the type 1090measuring instrument from du Pont de Nemours & Co., heating rate 20K/minute.

EXAMPLE 1 (COMPARISON EXAMPLE)

The coating solutions for the photopolymerizable layers are composed ofthe following components, in parts by weight:

    ______________________________________                                                        Parts by weight                                                                        Ma-                                                                           gen-                                                 Constituent:      Cyan   ta     Yellow Black                                  ______________________________________                                        Dipentaerythritol pentaacrylate                                                                 39.0   35.5   38.2   36.1                                   2-Diphenylyl-(4)-4,6-bis-                                                     trichloromethyl-s-triazine                                                                      9.8    7.8    9.5    9.6                                    Polyvinyl formal  31.3   36.5   35.4   28.0                                   (Formvar ® 12/85)                                                         Hostaperm ® Blue B2G                                                                        19.0   --     --     --                                     (C.I. 74,160)                                                                 Permanent Crimson FBB                                                                           --     18.5   --     --                                     (C.I. 12,485)                                                                 Permanent Yellow GR                                                                             --     0.7    16.4   --                                     (C.I. 21,100)                                                                 Carbon black (Printex ® 25)                                                                 0.4    0.5    --     24.8                                   Silicone oil (Edaplan ® LA 411)                                                             0.5    0.5    0.5    0.6                                    ______________________________________                                    

Each of the four mixtures was dissolved in a solvent mixture of 1000parts by weight of tetrahydrofuran, 680 pans by weight of1-methoxy-2-propanol and 190 parts by weight of gamma-butyrolactone.

The pigments are dispersed beforehand with a part of the binder and thebutyrolactone. The mean particle size is below 0.2 μm. The dispersionand the remaining constituents are mixed and applied to a 50 μm thick,biaxially stretched and thermofixed polyethylene terephthalate sheetwhich has been pretreated on both sides for improving the adhesion(Melinex® 505). The layers are dried at 70° C. The layer weights arebetween 0.6 and 0.8 g/m².

The solution of the adhesive layer is composed as follows:

    ______________________________________                                        Constituent              Parts by weight                                      ______________________________________                                        95:5 vinyl acetate/crotonic acid                                                                       96.6                                                 copolymer (Mowilith ® Ct5)                                                Polyvinyl methyl ether (Lutonal ® M40)                                                             1.9                                                  Sodium sulfite           1.4                                                  Water                    520.0                                                Ethanol                  43.0                                                 Aqueous ammonia, 25%     8.5                                                  ______________________________________                                    

The solution is applied to the dry photopolymerizable layers. Afterdrying, the layer weight of the adhesive layer is 6.5 g/m².

One of the sheets prepared in this way, for example the cyan colorsheet, is laminated at 85° C. to plastic-coated special paper andexposed under the cyan color separation film. The support iscontinuously peeled off by hand under an angle of 180°. The adhesivelayer and the positive cyan image remain on the paper, and the furtherphotopolymerizable color layers are successively laminated thereto andprocessed in the same way.

Example 2 (Comparison Example)

The composition of the coating solutions for the photopolymerizablelayers is the same as in Example 1, but the photoinitiator is replacedin each case by the same quantity of2,3-bis-(4-methoxyphenyl)-quinoxaline. The composition of theadhesion-promoting solution and the further processing are not changed.

In both comparison examples, a tonal value range from 2 to 98 % can bereached for all colors in a screen of 60 lines/cm, i.e. the screen dots,whose size corresponds to the indicated area coverage in %, are stillreproduced. As a measure of the background coloration, the opticaldensity in the non-image areas is determined by means of a densitometer.For this purpose, a color sheet is laminated in the manner described tothe receiving sheet and exposed for the optimum exposure time,determined beforehand, i.e. the exposure time at which the greatesttonal value range is reached. To intensify the measuring effect, theprocedure is, after the support has been peeled off, repeated a furtherthree times with color sheets of the same color. The optical density (D)of the image receiver sheet without proofing image, which is allocatedthe value zero, serves as a reference for measuring the backgroundcoloration. For the colors cyan (C), magenta (M), yellow (Y) and black(K), the following optical densities (D) for the image background aremeasured, with four plies in each case:

    ______________________________________                                        1    C      M       Y    K     2   C    M    Y    K                           ______________________________________                                        D    0.03   0.07    0.08 0.00  D   0.03 0.07 0.13 0.00                        ______________________________________                                    

The high optical densities for magenta and yellow show that thebackground stain of the four-colored proofing image is to be ascribedabove all to these two colors. Density values of more than 0.02 arealready clearly perceptible visually and hence interfere with the colorimpression which is decisive for a color-proofing method.

Example 3

150 parts by weight of a solution composed of 20.7 parts by weight oftert-butylperoxy 2-ethylhexanoate, 743 parts by weight of vinyl acetate,318 parts by weight of vinyl C₉ -alkanoate (Veova® 9), 60 parts byweight of crotonic acid and 66 parts by weight of isopropanol areincipiently polymerized at 70° C. On reaching 78° C., the residualmonomer solution is metered in over a period of four hours. After afinal polymerization phase of one hour, the solvent is distilled off.After cooling, the polymer is granulated. It is designated as terpolymerNo. 1 and contains the following monomer proportions:

    ______________________________________                                        Vinyl acetate            66.5%                                                Veova 9                  28.5%                                                Crotonic acid             5.0                                                 Viscosity (20% solution of the polymer in                                                               9.16 mPas                                           ethyl acetate):                                                               Glass transition point (Tg): 37° C.                                    ______________________________________                                    

The following solution of adhesive layer is in each case applied to thephotopolymerizable layer of color-proofing films in the colors yellowand magenta from Example 1, and dried:

    ______________________________________                                        Constituent       Parts by weight                                             ______________________________________                                        Terpolymer No. 1  96.6                                                        Lutonal M 40      1.9                                                         Sodium sulfite    1.4                                                         Water             520.0                                                       Ethanol           43.0                                                        Aqueous ammonia, 25%                                                                            8.5                                                         ______________________________________                                    

The layer weight of the dry adhesive layer is 6.5 g/m².

The color-proofing films thus obtained are each processed in the mannerdescribed under Example 1 to give a single-color, four-ply image. Thetonal value range is 4 to 96 %. For the background stain, the followingoptical densities (D) are measured:

    ______________________________________                                                       M      Y                                                       ______________________________________                                        D              0.02   0.06                                                    ______________________________________                                    

For magenta, a significant reduction of the background stain, and aslight reduction for yellow, can be achieved as compared with Examples 1and 2.

Example 4

For the adhesive layer, a terpolymer (No. 2) is used which has the samecomposition as the terpolymer No. 1, but a lower molecular weight:

Viscosity (20% solution of the polymer in ethyl acetate): 5.52 mPasGlass transition point: 36° C.

The solution of the adhesive layer, which is applied to thephotopolymerizable layer of color-proofing films for the colors magentaand yellow from Example 1, has the following composition:

    ______________________________________                                        Constituent       Parts by weight                                             ______________________________________                                        Terpolymer No. 2  96.6                                                        Lutonal ® M 40                                                                              1.9                                                         Sodium sulfite    1.4                                                         Water             520.0                                                       Ethanol           43.0                                                        Aqueous ammonia, 25%                                                                            8.5                                                         ______________________________________                                    

The layer weight of the dry adhesive layer is 6.5 g/m².

The color-proofing films thus obtained are each processed in the mannerdescribed under Example 1 to give a single-color, four-ply image.

    ______________________________________                                                          M        Y                                                  ______________________________________                                        D                 0.01     0.02                                               Tonal value range 10-85%   4-95%                                              ______________________________________                                    

The use of the terpolymer No. 2 gives a particularly effective reductionin background stain. The adhesion between the photopolymerizable layerand the adhesive layer decreases generally with the molecular weight ofthe polymer present in the adhesive layer. However, an unduly lowadhesion between photopolymerizable layer and adhesive layer leads, asshown by Example 4, to a tonal value range which is no longer sufficientfor the color-proofing method.

Example 5

The following adhesive layer is applied to the photopolymerizable layerof a magenta color-proofing film from Example 1, and dried:

    ______________________________________                                        Constituent       Parts by weight                                             ______________________________________                                        Terpolymer No. 2  64.4                                                        Mowilith Ct 5     32.2                                                        Lutonal ® M 40                                                                              1.9                                                         Sodium sulfite    1.4                                                         Water             520.0                                                       Ethanol           43.0                                                        Aqueous ammonia, 25%                                                                            8.5                                                         ______________________________________                                    

The layer weight of the dry adhesive layer is 6.5 g/m².

The color-proofing films thus obtained are each processed in the mannerdescribed under Example I to give a single-color, four-ply image. In thesingle-color image comprising four plies, the optical density of theimage background is D=0.02, and the tonal value range is 2 to 97 %.

Example 6

As described in Example 3, the terpolymer No. 3 is prepared from thefollowing starting substances:

    ______________________________________                                        Monomer proportions                                                           Vinyl acetate            76.0%                                                Veova ® 9 (vinyl C.sub.9 -alkanoate)                                                               19.0%                                                Crotonic acid             5.0%                                                Viscosity (20% solution of the polymer in                                                               9.20 mPas                                           ethyl acetate):                                                               Glass transition point: 39° C.                                         ______________________________________                                    

Composition of the solution of adhesive layer:

    ______________________________________                                        Constituent       Parts by weight                                             ______________________________________                                        Terpolymer No. 3  96.6                                                        Lutonal M 40      1.9                                                         Sodium sulfite    1.4                                                         Water             520.0                                                       Ethanol           43.0                                                        Aqueous ammonia, 25%                                                                            8.5                                                         ______________________________________                                    

The solution of adhesive layer is applied to the photopolymerizablelayer of color-proofing films for the colon magenta and yellow fromExamples 1 and 2, and dried. The layer weight of the dry adhesive layeris 6.5 g/m².

As described in detail in Example 1, single-color images comprising fourplies of the particular color are prepared. The following opticaldensities are measured for the background stain of the non-image areas:

    ______________________________________                                        1      M          Y      2       M    Y                                       ______________________________________                                        D      0.02       0.06   D       0.02 0.08                                    ______________________________________                                    

The tonal value range is 2-98 % in both cases. With the same reductionin the background stain as in Example 3, the tonal value range is heregreater and corresponds to the quality obtained in Examples 1 and 2.

Example 7

A terpolymer is prepared analogously to the instructions given inExample 3 from the following components and designated terpolymer No. 4:

    ______________________________________                                        Monomer proportions:                                                          Vinyl acetate            76.0%                                                Veova 10 (vinyl C.sub.10 -alkanoate)                                                                   19.0%                                                Crotonic acid             5.0%                                                Viscosity (20% solution of the polymer                                                                  9.10 mPas                                           in ethyl acetate):                                                            Glass transition point: 41° C.                                         ______________________________________                                    

Composition of the solution of adhesive layer:

    ______________________________________                                        Constituent       Parts by weight                                             ______________________________________                                        Terpolymer No. 4  96.6                                                        Lutonal M 40      1.9                                                         Sodium sulfite    1.4                                                         Water             520.0                                                       Ethanol           43.0                                                        Aqueous ammonia, 25%                                                                            8.5                                                         ______________________________________                                    

The solution of adhesive layer is applied to the photopolymerizablelayer of color-proofing films in the color magenta from Example 1, anddried. The layer weight of the dry adhesive layer is 6.5 g/m².

As described in detail in Example 1, single-color images comprising fourplies of the particular color are prepared. For the background stain ofthe non-image areas, an optical density of D=0.03 is measured, the tonalvalue range is 2 to 98%.

Example 8

A solution of adhesive layer of the following composition is applied toa support which is dimensionally stable when hot (polyester film fromICI, type Melinex 516, thickness: 50 μm), and dried:

    ______________________________________                                        Constituent            Parts by weight                                        ______________________________________                                        80:20 vinyl acetate/vinyl laurate copolymer                                                          10.0                                                   (Vinnapas ® B100/20VL)                                                    Polyvinyl acetate (Vinnapas ® B100)                                                              10.0                                                   n-Butyl acetate        80.0                                                   ______________________________________                                    

This adhesive film is laminated at 85° C. to a receiving sheet of paper.The support is peeled off, and the adhesive layer remains on thereceiving sheet. To this layer, a magenta color-proofing film, withoutan adhesive layer, according to Example 1 is laminated, likewise at 85 °C., and exposed under the corresponding color separation. After thecolor-proofing layer support has been peeled off, the single image forthe color magenta is obtained. This procedure is repeated until foursuperposed single images are also present in this example. The opticaldensity of the image background is D=0.02, and the tonal value range is2-98%.

We claim:
 1. A method for the production of a multicolored image, whichcomprises:(1) laminating a photosensitive material under pressure ontoan image-receiving material, wherein the photosensitive materialcomprises:(A) a transparent, flexible support, (B) a photopolymerizablelayer on (A) comprising:(B1) a polymeric binder, (B2) a compoundpolymerizable by a free-radical mechanism, (B3) a compound which iscapable of initiating the polymerization of (B2) under the action ofactinic light, and (B4) a dye or colored pigment in a primary color ofmulticolor printing, and (C) a thermoplastic, heat-activatable adhesivelayer on the photopolymerizable layer, wherein the adhesive layer (C)comprises at least one polymer which contains units (C1) with aliphaticside chains having at least 5 carbon atoms, (2) exposing thephotosensitive material imagewise through the film support with a colorseparation, (3) peeling the support together with the exposed areas offfrom the image-receiving material to produce a first positive image in aprimary color, and (4) repeating the steps (1)-(3) with at least onefurther color separation, the exposure being carried out in registerwith the first primary-color image on the image-receiving materialwherein the units (C1) are of the formula I ##STR4## in which R¹ is analiphatic radical having at least 5 carbon atoms, X is ##STR5## R² is Hor CH₃ and R³ is H or an alkyl group having 1 to 2 carbon atoms.
 2. Amethod for the production of a multicolored image, which comprises:(1)applying a thermoplastic, heat-activatable adhesive layer onto animage-receiving material, wherein the adhesive layer comprises at leastone polymer which contains units (C1) with aliphatic side chains havingat least 5 carbon atoms, (2) laminating a photosensitive materialcomprising a transparent, flexible support and a photopolymerizablelayer with the photopolymerizable layer onto the adhesive layer, whereinthe photopolymerizable layer comprises:(a) a polymeric binder, (b) acompound polymerizable by a free-radical mechanism, (c) a compound whichis capable of initiating the polymerization of (b) under action ofactinic light, and (d) a dye or colored pigment in a primary color ofmulticolor printing, and (3) exposing the photopolymerizable layerimagewise through the film support with a color separation, (4) peelingthe support together with the exposed areas off from the image-receivingmaterial to produce a first positive image in a primary color, and (5)repeating the steps (1)-(4) with at least one further color separation,the exposure being carried out in register with the first primary-colorimage produced on the image-receiving material wherein the units (C1)are of the formula I ##STR6## in which R¹ is an aliphatic radical havingat least 5 carbon atoms, X is ##STR7## R² is H or CH₃ and R³ is H or analkyl group having 1 or 2 carbon atoms.
 3. The method as claimed inclaim 1 or 2, wherein the polymer present in the adhesive layer (C) is acopolymer of units (C1) and units (C2) of the formula II ##STR8## inwhich R is an aliphatic radical having 1 to 4 carbon atoms and the othersymbols are as defined in claim
 2. 4. The method as claimed in claim 3,wherein the polymer present in the adhesive layer (C) additionallycontains units (C3) which have been formed from an α,β-unsaturatedcarboxylic acid.
 5. The method as claimed in claim 1 or 2, wherein thetransparent support (A) is a polyester film.
 6. The method as claimed inclaim 1, wherein the thermoplastic adhesive layer is applied directly tothe photopolymerizable layer from a dispersant, solvent or solventmixture which does not dissolve the photopolymerizable layer, and thendried.
 7. The method as claimed in claim 1, wherein the thermoplasticadhesive layer is applied to a temporary film support and transferredtherefrom to the photopolymerizable layer or to the image-receivingmaterial by lamination and then peeled-off of the temporary filmsupport.
 8. The method as claimed in claim 1 or 2, wherein thelamination is carried out at a temperature of 60° to 130° C.
 9. Themethod as claimed in claim 1 or 2, wherein the dyes or colored pigmentsare selected from the group consisting of cyan, magenta, yellow andblack.
 10. The method as claimed in claim 1 or 2, wherein theimage-receiving material is paper.
 11. The method as claimed in claim 1or 2, wherein the film support is peeled-off from the image-receivingmaterial at an angle of at least 90°.
 12. The method as claimed in claim1 or 2, wherein the film support is peeled off from the image-receivingmaterial at an angle of about 180°.
 13. The method as claimed in claim 1or 2, wherein the film support is manually peeled-off from theimage-receiving material.